Valves, in particular, butterfly valves having a disk rotatably mounted within a bore of a valve housing present numerous challenges in both their design and assembly. Valves according to the prior art are designed to be assembled from the outside of their housing. The disk is positioned within the bore and valve stems or shafts are inserted from outside of the housing into the bore to rotatably mount the disk within the housing. Such a design requires complicated seals and bonnets which must retain the shafts against the internal pressure of the valve. Advantage may be had by an improved valve design which does not suffer the disadvantages of valve according to the prior art.